M880 GC
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Maybe this might save a bit of grief working on these old mechanical pump systems, maybe not.
I am on pump #4 since I got my truck. It was sold with a "bad" pump. I am not driving this on the street yet but I have already bought 3 pumps, make that 2 one was defective out of the box, but maybe it wasn't defective after all.
I finally have one that is working as is should since saturday.
With the most recent pump I replaced the entire fuel line from the tank with 5/16" fuel line, this goes into a 5/16" clear housing filter (we are trying to learn here) then the pump, then a second fuel filter and finally all new lines up to the carb.
Works like it should.
Observations.
1. Primary filter only has a SMALL amount of fuel in it while running.
2. Secondary filter is mostly filled with gas, small air bubble in top.
3. You can feel the pump "ticking" when you touch the line or filter at idle.
4. Previous pump, cut open and found likley cause of check valve failure to be old rubber fuel line debris under check valve diaphragm, unconfirmed.
5. The pump has an inlet and outlet check valve, looks like low pressure is created at diaphragm during pump cycle, check valves allow fuel in, then pushed out on return stroke, but not to flow back into tank. My old one always seemed to loose prime, needed a splash of gas to get it woke up.
6. New pump hand cycled on the bench made a definet WHOOSH WHOOSH.
Didn't find much help in any manual. Other than hooking up a pressure gage which I do not own. And just R&R a ned pump with old line debris would have just ruined a new pump.
This old stuff needed refreshing in my diagnostic control system, me.
I am on pump #4 since I got my truck. It was sold with a "bad" pump. I am not driving this on the street yet but I have already bought 3 pumps, make that 2 one was defective out of the box, but maybe it wasn't defective after all.
I finally have one that is working as is should since saturday.
With the most recent pump I replaced the entire fuel line from the tank with 5/16" fuel line, this goes into a 5/16" clear housing filter (we are trying to learn here) then the pump, then a second fuel filter and finally all new lines up to the carb.
Works like it should.
Observations.
1. Primary filter only has a SMALL amount of fuel in it while running.
2. Secondary filter is mostly filled with gas, small air bubble in top.
3. You can feel the pump "ticking" when you touch the line or filter at idle.
4. Previous pump, cut open and found likley cause of check valve failure to be old rubber fuel line debris under check valve diaphragm, unconfirmed.
5. The pump has an inlet and outlet check valve, looks like low pressure is created at diaphragm during pump cycle, check valves allow fuel in, then pushed out on return stroke, but not to flow back into tank. My old one always seemed to loose prime, needed a splash of gas to get it woke up.
6. New pump hand cycled on the bench made a definet WHOOSH WHOOSH.
Didn't find much help in any manual. Other than hooking up a pressure gage which I do not own. And just R&R a ned pump with old line debris would have just ruined a new pump.
This old stuff needed refreshing in my diagnostic control system, me.